1. Field of the Invention
The instant disclosure relates to a manufacturing method of charge storage device; in particular, to a manufacturing method of capacitor lower electrode and a semiconductor storage device using the same.
2. Description of Related Art
Dynamic random access memory (DRAM) is one kind of widely used integrated circuit element. With the vigorous development of semiconductor industry, the dimension of integrated circuit elements nowadays range from micron size to submicron size. For DRAM, that is to say, the cross-sectional area of each capacitor and each gap between capacitors become smaller. Basically, the better operating capability of computer software becomes, the greater memory capacitance of computer hardware need. Facing up to the problem of the capacitor dimension become smaller, but the memory capacitance must be increased. The traditional method of manufacturing DRAM capacitors certainly needs to be improved.
Generally, the following methods are often used to increase capacitance to store the bits of data. The first method is to decrease the dielectric constant of the dielectric material. The second method is to decrease the thickness of the dielectric layer. The third method is to increase the electrode contact-surface area. However, in view of the resolution of pattern transfer is increased and the critical dimension of the line width is reduced. Limitation exists for improving lithography by only optical improvement.
In addition, MIM (Metal insulator Metal) capacitors basically a parasitic capacitor between the metal layers. Generally three or more reticles are used in the processing steps. In order to overcome its complex process, the design of DRAM will focus on a reduction in the number of reticles used.